Valve unit for vacuum operated palletizer lifting heads

ABSTRACT

A valve unit adapted for insertion in an air passage opening through the grid of a vacuum operated palletizer lifting head having a rectangular body with a pair of elongated faces on opposite sides thereof and a generally central aperture therethrough between the elongated faces to permit air to pass through the body. The body has in one of its elongated faces a concave valve seat surrounding the aperture. The valve unit also has a valve member and means movably supporting the same on the body adjacent the valve seat, the valve member being a thin, resilient element adapted to be flexibly shiftable between an open position spaced from the valve seat and a closed position seated against the valve seat and shaped to conform to the concavity thereof. Means are provided around the periphery of the body for forming a seal between the body and the grid of the palletizer.

United States Patent Dahlquist et al.

[54] VALVE UNIT FOR VACUUM OPERATED PALLETIZER LIFTING HEADS [72]Inventors: Ernst A. Dahlquist, Grand Rapids; Stanley J. Polakowski,Kalamazoo; Teunis Vaalburg, Ann Arbor, all of Mich.

[73] Assignee: Rapistan Incorporated, Grand Rapids, Mich.

[22] Filed: Sept. 4, 1970 211 Appl. No.: 69,688

[52] U.S. Cl. ..137/454.2, 137/519, 137/526, 137/525, l37/512.1, 294/64R [51] Int. Cl. ..Fl6k 15/02, F16]: 15/14 [58] Field of Search.294/64 R,65; 137/4542, 454.4, 137/4546, 512.1, 519, 526, 525

[56] References Cited UNITED STATES PATENTS 2,011,088 8/1935 Shindel..137/525 2,960,364 11/1960 Herzog ..294/65 2,970,608 2/1961 Doeg..137/525 X 51 Oct. 17,1972

3,109,451 11/1963 Mihalakis ..137/525 X 3,123,096 3/1964 Notaro et a1 137/525 3,523,707 8/1970 Roth ..294/65 Primary Examiner-Robert G. NilsonAttorney-Price, Heneveld, l-luizenga & Cooper 5 7] ABSTRACT A valve unitadapted for insertion in an air passage opening through the grid of avacuum operated palletizer lifting head having a rectangular body with apair of elongated faces on opposite sides thereof and a generallycentral aperture therethrough between the elongated faces to permit airto pass through the body. The body has in one of its elongated faces aconcave valve seat surrounding the aperture. The valve unit also has avalve member and means movably supporting the same on the body adjacentthe valve seat, the valve member being a thin, resilient element adaptedto be flexibly shiftable between an open position spaced from the valveseat and a closed position seated against the valve seat and shaped toconform to the concavity thereof. Means are provided around theperiphery of the body for forming a seal between the body and the gridof the palletizer.

6 Claims, 9 Drawing Figures VALVE UNIT FOR VACUUM OPERATED PALLETIZERLIFTING HEADS BACKGROUND OF THE INVENTION This invention relates tovacuum operated palletizers and, more particularly, to improved valvedevices for use therein.

In the palletizer art, articles such as case goods are automaticallyarranged on a conveyor surface in groups and then, by a head havingvacuum creating equipment, the articles as a group, are lifted from theconveyor surface and loaded onto a pallet. Such a group of articles iscalled a tier and a number of tiers are stacked, one upon another, toform a pallet load. This system works satisfactorily when the articlesare such that the articles in every tier can be so arranged that thetiers perimeter has the same dimensions and geometry and no internalchimneys or voids exist within the tier. However, forstability of thepallet load, alternate tiers should have different patterns so that thearticles of one tier overlap the articles of the tier on which it rests.This ties the load together. Frequently, internal chimneys are formedwhich are in different positions in each tier. The problem ofnon-identical tier geometry occurs under some operating circumstanceswhen the same palletizer is used, first for articles of one size andshape and then for articles of another size and shape.

Conventionally, the vacuum lift heads of palletizers are built to havean over-all intake opening sized to fit the tier of greatest perimeter.The opening is normally subdivided by a grid or other means into aplurality of subopenings or individual air passages. Certain groupingsof articles leave substantial areas at the perimeter of the tier whichare not covered by the articles. Also the chimneys remain open. Oftenthe volume of air which can enter through these unused openings is sogreat that the head must have excessive air pumping capacity to createsufficient vacuum to lift the articles. In some cases, even thisexpedient is inadequate. Such an arrangement is initially expensive andbulky. It is also both expensive and noisy to operate. Further, evenwith excessive air pumping capacity, the equipment can only handlerelatively minor variations in tier size.

To overcome these problems, various devices have been employed includingflexible curtains which close in around the sides of the articles. Thissystem works reasonably well if the shape of the perimeter is reasonablyregular and does not involve any significant indentations or recesses.It does not solve the problem of internal chimneys.

Another solution has been the use of individual valves, shaped somewhatlike cuff-links, located in the individual air passages. These remainclosed until opened by contact with the articles. These have not beenentirely satisfactory. To prevent them from opening in response to thevacuum alone, they have to be heavy and their weight pressing down onthe articles is added to that of the articles. In effect, this reducesthe efficiency of the equipment by reducing its pay-load capacity,collectively, the weight of these valves represents a substantialreduction in equipment capacity. Also, should the edge of an articlehappen to contact the valve and open it, even though the article isclosing off only a relatively small portion of the entire air passage,large volumes of air are allowed to enter. When a number of valves areso affected, the capacity of the equipment is seriously impaired.

ln co-pending, co-assigned application Ser. No. 781,823, filed Dec. 6,1968, now US. Pat. No. 3,598,439, an improved vacuum operated palletizerlifting device is disclosed which solves these problems. The deviceconsists of a lifting head having a primary chamber from which air isexhausted, the bottom of which is formed by a grate creating a number ofsmall individual air passages. A number of these individual air passagesare equipped with individually operable valves which open and close inresponse to a predetermined amount of air pressure differential acrossthe valves. The valves close to shut off the flow of air into theprimary chamber through those individual air passages not closed off bythe articles to be lifted. However, as these valves are permanentlymounted in the grate, a large number are required in order to be usefulwith tiers differing greatly in tier geometry, i.e., tier perimeter andchimney locations. Furthermore, these valves add significantly to thecost and complexity of manufacture of the palletizer heads since notonly must the valves be permanently mounted, but also the heads must becustomized as to valve locations for the anticipated range of tierperimeter's and chimney locations for which the palletizer will be used.While valves could be mounted in all or most of the grate air passagesto accommodate any chimney locations or greatly varying tier perimeters,this would be impractical and unduly expensive as well as decreasing thelifting capacity of the lifting head.

Accordingly, it would be desirable to eliminate these disadvantages ofthe above device while still maintain ing its utility for solving theproblem in the art associated with non-identical tier geometry.

SUMMARY OF THE INlVENTlON According to the present invention there isprovided an improvement in vacuum operated palletizers which comprises avalve unit adapted to be easily inserted in or removed from the grid airpassages in the lifting heads of such palletizers, and which opens andcloses in response to a predetermined amount of air pressuredifferential across the valve. These valve units, which can beinexpensively, uniformly mass produced, can be easily inserted inpalletizer lifting head grids just prior to use in arrangements toaccommodate anticipated tier perimeters and chimney locations and can beeasily relocated when tier perimeters or chimney locations changegreatly. Thus, a minimum number of valve units can be used for eachpalletizer head and can be rearranged easily when necessary rather thanhaving to provide a great number of permanently installed valves toaccommodate all possible tier geometries. The novel valve unit comprisesa body of rectangular configuration having a pair of elongated faces onopposite sides thereof and a generally central aperture therethroughbetween the elongated faces to permit air to pass through the body, thebody having in one of the elongated faces thereof a concave valve seatsurrounding the aperture. A thin, resilient valve member is movablysupported on the body adjacent the valve seat adapted to flexibly shiftbetween an open position spaced from the valve seat and a closedposition seated against the valve seat shaped to conform to theconcavity of the valve seat. Surrounding the body around the facesadjacent the two elongated faces are means, preferably an elasticO-ring, for forming a seal between the body and the palletizer head gridsurrounding each air passage defined by it when the valve unit isinserted in the grid.

Valves are inserted in the perimetrical areas of the grate according tothe anticipated range of tier perimeters and in those areas wherechimneys may be formed. When the palletizer is operated, all of the airpassages are not closed by the presence of an article are automaticallyclosed off by the valves. This permits the vacuum lift headautomatically to adjust the over-all shape of its airintake to that ofthe tier of articles and to limit its air intake only to those airpassages covered by the presence of an article. The construction of thevalve is such that it adds substantially no weight to the head, appliesno load to the articles acting against the effect of the vacuum and ispositive in its closing action when the required air pressuredifferential is attained. When tiers are to be moved with perimeters orchimney locations differing from those provided for, the valves can beeasily and quickly relocated or valves added or removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom oblique view of avalve unit of the present invention;

FIG. 2 is a sectional elevation view of a valve unit with valve takenalong the plane IIII of FIG. 3;

FIG. 3 is a bottom view of a valve unit without valve;

FIG. 4 is an end view of a valve unit;

FIG. 5 is a side elevational view of a vacuum operated lifting head;

FIG. 6 is a fragmentary, bottom view of one quadrant of the lifting headof FIG. 5 equipped with valve units of the present invention;

FIG. 7 is a fragmentary, top oblique view of a section of the grid ofthe lifting head of FIG. 5;

FIG. 8 is an'enlarged sectional elevation view taken along the planeVIII-VIII of FIG. 6; and

FIG. 9 is a schematic view illustrating the operation of a valve unit ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to FIG.1, a bottom oblique view of a valve unit 10 of the present invention isshown. The valve unit body 11 has a central aperture 12 therethrough anda concave valve seat 13 surrounds this aperture. Bosses 14 depend frombody 11 at both ends of concave valve seat 13. The bosses are at eachend of the valve body. The side edges of the bosses are preferablyspaced from the longitudinal edges of the body 11. Between the bossesthe lower face of the body is formed into the long shallow concavityforming the valve seat 13.

Thin resilient valve member 15 is movably supported adjacent valve seat13 by support means 17 which can be any suitable fasteners, pins, drivescrews, etc., so long as the ends of the valve member are free to slidelengthwise on their stems or shafts in response to the flexing of thevalve. Valve member 15 may be made of any lightweight resilient materialwhich also has sufficient strength to withstand the pressures exertedagainst it when it is in the sealing or closure position and to resistshifting to closed position until a predetermined pressure differentialacross the valve exists. The material should also be resistant tofatigue failure resulting from frequent flexing as the valve opens andcloses. A suitable material for this member is a thin spring steel.Valve member 15 is free to collapse and to conform to the concavity ofvalve seat 13 since the openings 20 are over-size with respect to thesupport means 17. Preferably, slight ribs or fulcrum crimps 16 areprovided near both ends'of valve member 15 to minimize friction againstbosses 14 when the valve member is flexed against valve seat 13 orreleased to shift to its open position. The width of valve member 15must be such as to completely cover the central aperture 12 to form aneffective seal and with enough overlap on concave valve seat 13 tosupport the valve member when it is in the air sealing position. Theconcavity of valve seat 13 improves the air seal attained when valvemember 15 is in the closed position.

Around the periphery of body 11 is sealing gasket 18 which can be, forexample, an elastic O-ring. This gasket forms a seal between the valveunit and the grid surrounding the air passages in the palletizer liftinghead and can be held in place in the valve body by positioning it in aperipheral groove 19 around body 11. FIGS. 2, 3 and 4 more clearlyillustrate the construction of valve unit 10.

In FIG. 5, a side elevation view of a vacuum operated lifting head 30 isshown. This head consists of a rectangular frame 31, an air pump orblower chamber 32 and a motor 33 for the blower. Clamped to the loweredge of the frame 31 is a detachable subframe 34. The attachment is madeby the fasteners 35. It will be understood that the top of the frame 31is closed except for the opening into the blower chamber 32 and a reliefport 37. This forms a primary chamber 36 above the subframe 34. Therelief port 37 communicates with the primary chamber. Air exhausted bythe fan or blower exits via the blast port 38 which is equipped with aclosure gate. All of the preceding structure is conventional and furtherdescription of it is unnecessary.

It will be understood that in the palletizer assembly, the entire headis mounted by suitable means by which it can be raised and lowered and,in addition, has means to guide it for both vertical and horizontalmovement. This again is conventional, forms no part of the inventionand, therefore, is not illustrated.

One quadrant of the lower face of the lifting head is illustrated inFIG. 6 which shows the subframe 34 and a main grate 40, having on itsside an auxiliary grate 41. The grates form a back stop for articlesheld against the head by air pressure differential. The main andauxiliary grates are formed of bars of rectangular cross section whichintersect to form a rigid structure characterized by a plurality ofindividual air passages or openings 42 of generally rectangular shape.That portion of the lower face of the head not occupied by the main andauxiliary grates is closed off as by the closure plate 43 and theclosure strip 44.

It will be recognized that other constructions could be utilized for thegrate. For example, it could be a single sheet of material with thedepending structure supplied by the bars formed by sharply defineddepending ridges surrounding the recesses. The sheet material would havean air passage in each of the recesses. Irrespective of whether thismember is constructed as the grate illustrated or made in some othermanner, it is a perforate member which forms a stop for the articles 5.and provides numerous individual air passages opening into the primarychamber.

Referring first to the auxiliary grate 41 (FIG. 6), it will be notedthat all of the openings 42 in the central portion of this grate areoccupied by valve units 10, one in each of the openings. At the end ofthe grate and on each side of the valve units, the openings are closedby seals 51. The seals 51 are formed of a suitable material such as afoam rubber which is compressible and project beyond the face of thegrate for contact with articles. These seals prevent flow of airparallelto the face of the grate between the grate and the articles of the tier.The seals 51 collectively form gaskets which isolate thevalved openingsor air passages from those which are not valved. It will be noted that asimilar arrangement is provided along the side of the main grate 40.

Arranged in the'center 52 of the grate 40 are additional valve units 10.The purpose of these will be explained more fully hereinafter. Except inthe areas where either the gaskets 51 or the valve units are provided,the openings 42 in the grate are free of ob struction, permitting air topass through the grate into the primary chamber 36 under the inducementof the fan. When the fan is operating and the blast port is open, thereis a differential in air pressure between the air below the grate andthat within the primary chamber.

The main grate 40 and the auxiliary grates 41 are both seated within thesubframe 34 and below the main frame 31 and, thus, below the primarychamber 36.

Since each valve unit 10 is a separate, self-contained assemblyoccupying only one of the openings 42, they can be arranged in variouspatterns within the grates, and the number employed can be limited tothose necessary to satisfy the operating circumstances of the liftinghead. The valve units 10 are easily inserted in any of the grateopenings 42 by applying slight pressure to wedge the sealing means 18against the grate wall surrounding the openings 42 and can be easilypulled out and eliminated or relocated as needed. FIG. 7 is an obliqueview of a portion of the top of grid 40 illustrating crimps 45, thepurpose of which is to form stops to keep the valve units 10 from beingdrawn upward out of position from the grate due to the vacuum suction.Any other suitable restraining means could be employed as well. FIG. 8illustrates a valve unit 10 properly positioned in an opening 42 ofgrate 40 and seated against crimps 45. v

In the particular arrangement illustrated in FIG. 6, a pattern of thevalve units 10 is arranged about the perimeter of the opening in thehead. The fact that along one side, the rows of valves are arranged insideby-side relationship and along the other side each row is spacedfrom the adjacent row by a row of seals 51 is illustrative only. Anyother pattern arrangement suitable to the operating circumstances of thehead could be utilized.

The valve units at the center 52 of grate 40 are located to coincidewith the chimneys which may be formed in the tier patterns to beemployed.

OPERATION OF THE INVENTION The head 30 is lowered until the grate andthe seals 51 contact the articles of the. tier. The seals 51 projectslightly beyond the bottom face of the grate to have an effectivesealing action against the articles. This gasket forming action may befurther increased by having the rows of seals projecting progressivelygreater distances from the grate, the more remote the seals are from thecenterof the grate. This is particularly important in effecting a sealadjacent the edge of the tier where the top of an article may slopedownwardly away from the grate. In this type of situation, the greaterprojection of the peripheral seals will assure an effective barrier tolateral air flow. This will enable even those air passages at theperiphery of the tier to exert full lifting capacity on the articles.When a number of air passages are so affected, the result is a markedincrease in the efficiency of the equipment.

With the fan operating and the: blast gate open, contact between thegrate and the articles immediately closes off the air flow through thoseof the openings covered by the articles. Until this happens, the airpressure differential across the grate, even with the fan operating andthe blast gate open, is not enough to cause the valve units 10 to closebecause the total number of air passages to openings in the grate bywhich air can enter the primary chamber provides an air flow capacity ofsufficient volume that the air pressure differential required to closethe valves cannot be obtained. However, the closing of a number of theopenings by the articles upsets this balance and the air depend upon thedegree to which the obstruction is effective in reducing the air flow.The particular air pressure differential at which the valve units willclose can be varied in several ways such as by selection of thestiffness of the material used in making the valve member. This can becontrolled, for example, by the particular alloy used or by selection ofa thinner or thicker material. The maximum vacuum which can be generatedin the primary chamber will of course be determined by the capacity ofthe fan. A fan which can generate a differential of 25-26 inches ofwater has been found satisfactory. It has also been ascertained that avalve designed to close when the pressure differential between the valveand valve member reaches 1 1 inches of water will close, if theeffective air intake area to the opening is reduced to 0.2 of a squareinch of effective air intake area when the vacuum in the prim arychamber has avalue of approximately 20 inches of water.

It is desirable that the valve remain closed unless a substantialportion of the opening is obstructed by an article. However, once theobstruction is such that the threshold pressure differential is notattained, the valve must remain open. Otherwise, insufficient openingswill remain operative to retain the: peripheral articles against thegrate. It is at this point that the gaskets formed by the seals 51become important. They form an effective seal against the articles.Those of the openings closed by articles and within areas surrounded bythe gaskets will generate maximum air pressure differential betweenambient and the primary chamber and thus maximum lifting capacity.

The principle of operation of the individual valve units is illustratedin FIG. 9. The valve member in the open position creates a pair of airpassages 60 and 60a (FIG. 9), one on each side. The flow of air throughthese passages is indicated by the arrows A. As the pressuredifferential between the primary chamber and the air passage increases,the velocity of the air increases as it bypasses the valve through thepassages 60 and 60a. As the pressure differential increases, theunbalance between the pressure acting against the upper face 61 of thevalve and that acting against the lower face of the valve (arrows B)increases. When this pressure differential reaches a certain level, theresistance of the valve member to collapse is overcome and the valvecloses by conforming to the concave valve seat 13. When the pressuredifferential falls below a certain level, the valve member 15 willautomatically snap open.

To release the load, the gate on the blast port 38 is closed. Thisimmediately reduces the fans air pumping capacity and the pressuredifferential between the primary chamber and the air passages decreases.This effect can be accelerated by opening the relief port 37 to bleedair into the primary chamber. When the air pressure differential dropsbelow than necessary to support the tier of articles, they will bereleased.

Selection of a pressure differential value for effecting closure of thevalve depends upon various design factors and the operatingcircumstances of the lift head. It is important that the valve not be sosensitive that it fails to stay open when the air passage is blocked bythe presence of an article since this could seriously impair the liftingcapacity of the head. It also must close when any significant portion ofair passage remains unobstructed.

The invention provides inexpensive, mass producible valve units whichare adapted to be easily inserted in the grids of palletizer vacuumlifting heads which permit the lifting head to automatically adjustitself to accommodate a wide variety of load shapes and sizes. They alsopermit the use of a fan having only that capacity necessary to lift atier of articles when substantially the entire bottom of the head isblocked off by articles because this is the condition which exists whenthe valve units are closed even though only a portion of the lower faceof the head is covered by the articles. Reducing the capacity of the fanreduces the initial cost, operating cost and the noise incident to itsuse. Further, irrespective of fan capacity, it permits much greatervariation in load size and shape than is possible without the valves.The fact that the valve units can be easily inserted and removed fromthe lifting head grids, minimizes the number of valve units required toadapt a lifting head to accommodate varying tier geometries as well aseliminating the need to manufacture lifting head grids with permanentvalves mounted therein, each having to be customized to accommodate theintended range of tier geometries. Further, each valve being a completeoperative assembly, the invention permits the modification of existinglifting heads to variable load capacity by the installation of valvesincorporating this invention.

While a preferred embodiment of the invention,

. sive property is claimed are defined as follows.

1. A valve unit adapted for insertion in an air passage opening throughthe grid of a vacuum operated palletizer lifting head comprising: arectangular body having a pair of elongated faces on opposite sidesthereof and a generally central aperture therethrough between said facesto permit air to pass through the body; said body having in one of saidfaces thereof a concave valve seat surrounding said aperture; a valvemember and means movably supporting the same on said body adjacent saidvalve seat, said valve member being a thin resilient element adapted tobe flexibly shiftable between an open position spaced from said valveseat and a closed position seated against said valve seat shaped toconform to the concavity thereof; and means around the periphery of saidbody for forming a seal between said body and said grid.

2. A valve unit of claim 1 wherein said valve member has fulcrum crimpsnear each end thereof which contact said body when said valve memberflexes between said open and closed positions to minimize frictionbetween said valve member and said body. 7 3. A valve unit of claim 2wherein said valve member is generally rectangular in configuration withopenings near each end thereof, said support means passing through saidopenings and said openings being oversize with respect to said supportmeans.

4. A valve unit of claim 3 wherein said valve member is made of springsteel.

5. A valve unit of claim 4 wherein said means around the periphery ofsaid body comprises a resilient O-ring.

6. A valve unit for automatically regulating the intake of air by thevacuum lifting head of a palletizer through one of the individual airintake passages of said head, said valve unit comprising: a body havinga main portion with an upper and a lower face and a boss depending fromsaid lower face thereof; that portion of said boss adjacent the centerof said body being formed into an elongated concave valve seat; anaperture extending through said body between said upper and lower facesand generally centered with respect to said concave valve seat; saidvalve seat extending outwardly from said aperture in all directions; athin flexible valve member and means at each end of said valve seatsupporting said valve member on said body; said valve member beingshiftable from an open position spaced from said valve seat to a closedposition pressed to said valve seat and conforming to its concave shape;and a resilient sealing gasket surrounding said body and projectingoutwardly therefrom.

1. A valve unit adapted for insertion in an air passage opening throughthe grid of a vacuum operated palletizer lifting head comprising: arectangular body having a pair of elongated faces on opposite sidesthereof and a generally central aperture therethrough between said facesto permit air to pass through the body; said body having in one of saidfaces thereof a concave valve seat surrounding said aperture; a valvemember and means movably supporting the same on said body adjacent saidvalve seat, said valve member being a thin resilient element adapted tobe flexibly shiftable between an open position spaced from said valveseat and a closed position seated against said valve seat shaped toconform to the concavity thereof; and means around the periphery of saidbody for forming a seal between said body and said grid.
 2. A valve unitof claim 1 wherein said valve member has fulcrum crimps near each endthereof which contact said body when said valve member flexes betweensaid open and closed positions to minimize friction between said valvemember and said body.
 3. A valve unit of claim 2 wherein said valvemember is generally rectangular in configuration with openings near eachend thereof, said support means passing through said openings and saidopenings being over-size with respect to said support means.
 4. A valveunit of claim 3 wherein said valve member is made of spring steel.
 5. Avalve unit of claim 4 wherein said means around the periphery of saidbody comprises a resilient O-ring.
 6. A valve unit for automaticallyregulating the intake of air by the vacuum lifting head of a palletizerthrough one of the individual air intake passages of said head, saidvalve unit comprising: a body having a main portion with an upper and alower face and a boss depending from said lower face thereof; thatportion of said boss adjacent the center of said body being formed intoan elongated concave valve seat; an aperture extending through said bodybetween said upper and lower faces and generally centered with respectto said concave valve seat; said valve seat extending outwardly fromsaid aperture in all directions; a thin flexible valve member and meansat each end of said valve seat suppoRting said valve member on saidbody; said valve member being shiftable from an open position spacedfrom said valve seat to a closed position pressed to said valve seat andconforming to its concave shape; and a resilient sealing gasketsurrounding said body and projecting outwardly therefrom.